The countries with the highest population growth also have the lowest per capita emissions.

Talks about "overpopulation" usually revolve or quickly devolve into demands for genocide of people deemed inferior, usually by their skin color not being white enough.

The argument that population is the main driver for emissions only holds true in the scope of leaving the global economic system unchanged and continue to maximize individual consumption as the primary indicator of "wellbeing".

The authors of the study you linked also conclude that rich nations should embrace population decline as a way to reduce emissions. Problem is when this gets to politicians they usually flip it around.